In conventional cheese making processes, micro-organisms and enzymes react with milk or milk products to form a curd. These conventional processes are typically batch processes in which the curd is formed in large vats. In conventional practice, to produce firm or hard cheeses, milk or a milk fraction is acidified to a point above the protein contors isoelectric point by bacteria and rennet (enzyme) or a rennet product, is thereafter added to produce an enzyme curd. All cheeses derive from the initial formation of either an acid curd, or an enzymatic curd. In conventional practice, the transformation of the protein content with fats and other constituents of a milk based feed is a slow process for either type.
U.S. Pat. Nos. 5,006,349 and 4,675,194 each disclose a process for producing a cheese product by instantaneously mixing a protein stream and an acid stream in a high energy resonating chamber. In certain examples in U.S. Pat. Nos. 5,006,349 and 4,675,194, rennet is mixed with the acid stream, but the pH exiting the Sonolator reactor is maintained at or below the isoelectric point of the proteins involved. Since inorganic reactions proceed much faster than organic reactions, the resulting curd is predominantly an acid curd which did not become firm in any of the examples set forth in the two patents. These were directed to markedly decreasing the time of curd formation and stipulated that the immediate curd was acidic at a pH below the isoelectric point, even if enzymes were introduced in the feed streams or stream concomitantly with the acid. This addressed making the softer cheeses and spreads such as Buttermilk, Neufchatel, Cream Cheese, Cottage and Whey cheeses. Having not experimentally made sonolated curd and cheese products above the isoelectric point, no basis was provided for determining what would happen for reactions above the isoelectric point.
However, in conventional cheese making utilizing enzymes it has been found in normal practice to first produce sufficient acid, via a bacterial culture before adding the rennet, to result in the best workable curd. The acid strips some of the bound calcium ions in the milk protein, and provides calcium ions that accelerate the action of the rennet. When to add the rennet has always been a matter of art. However, the pH is always quite some level above the isoelectric point.
One can visualize long chain intertwining protein molecules somewhat analagous to DNA being cleaved by rennet that destroys their solubility. Contrasted to this, an acid precipitated curd with most of calcium stripped would have a different configuration and properties.
As later elaborated, the final curd made by acid precipitation, as disclosed in U.S. Pat. Nos. 5,006,349 and 4,675,194, is bound to have different characteristics than an initial enzyme produced curd even though it is later reduced in pH by acid producing bacteria.
In the conventional cheese making processes, the practice involves much art, i.e. non-scientific efforts, in producing the various hard cheeses. Further, the resulting product is often times non-uniform, especially at a microscopic level. When one tries to make hard cheeses (or cheeses wherein the protein matrix can be worked mechanically or by the heat of transformation) by a one step process of acidification along with an enzyme (rennet) to or below the isoelectric point, one gets a combination of acid coagulum and enzyme coagulum, the extent of each, a function of temperature and time. The reaction rates of acids added with the calcium of a protein is from published data, greater than that of an enzyme. One concludes that the acid curd initially forms or controls and that the enzymatic action follows. Clearly the resulting structure must be different from that involved in first forming an enzymatic curd followed by acid transformation. The non-uniformity is attributable to both the uneven progressive bacterial activity in acidifying the milk protein and the non-uniform progressive action of the enzyme.
On the other hand, the U.S. Pat. Nos. 5,006,349 and 4,675,195 both disclose a method of making an acid curd based cheese. Even though enzyme rennet was used in some of the experimental runs, the dynamics of the chemistry and physics involved were simply not addressed in terms of producing enzyme curd cheeses.